INCLUSIONS Six types of HCF (university hospital, large or small public hospitals, private HCFs, referral centers for cancer, and a mixed group of local hospitals, long term care and post-op and rehabilitation facilities, and nursing homes in each of the 5 interregional coordination centers for infection control (CCLIN). All eligible HCWs working during the survey day will be included. A minimum of 2,100 HCW is required to properly estimate the rate of HCW with the minimum core of knowledge (p<0.05). Actually, a larger number of 5,000 to 10,000 participants should be included.